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ACOUSTIC TELEPHONE. No. 281,407. Patented July 17,1883.

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UNITED STATES ATENT OFFICE.

CHARLES SELDEN, OF ST. LOUIS, MISSOURI.

ACOUSTIC TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 281,407, dated July 17,1883.

Application filed April 2, 1883. (N0 model.)

To all whom it ntay concern.-

Be it known that I, CHARLES SELDEN, a citizen of the United States, and a resident of St. Louis, in the State of Missouri, have invented certainnew and useful Improvements in Acoustic Telephones, of which the following is a specification.

My invention relates to that class of telephones in which speech and sound are transmitted by mechanical vibrations through a cord, rod, or its equivalent, mechanically con necting two diaphragms or other vibratory surfaces, placed, respectively, at the points be tween which communication is desired. I have found by experiment that where a long line is used in this kind of telephonic connnunication, and the line is strung to high'tension, the weight or tension of the line puts such a strain 011 the diaphragm and makes it so rigid as to interfere seriously with the proper transmission and reception of speech.

One of the objects of my invention is to remove this difficulty; and to this end my invention consists in interposing between the line and the diaphragm a lever or equivalent mechani'cal device, which acts to reduce the strain of the line that is exerted uponthe diaphragm, the line for this purpose being attached to the shorter arm of the lever, while the longer arm thereof is connected with the diaphragm. Such an arrangement improves the action of the apparatus both in the transmission and reception of speech-in the first instance because the diaphragm is allowed freer and more unrestrained movement, its vibrations being, nevertheless, properly communicated to the line, and in the second instance because the vibrations of the line are communicated with an increased amplitude to the diaphragm, while at the same time the weight or strain of the line is not so great 011 said diaphragm.

The object of my invention is also to still further increase the efficiency of the device by the peculiar construction herein described, which consists, essentially, in mounting the le ver or its equivalent upon a second-diaphragm, which is affected simultaneously with the first and adds its effects to those of the first.

My invention further consists in certain improvements in details of construction, that will be specified in theclaims.

to be used for signaling purposes, one pole of said battery being connected, as indicated, with the ground, while the other is connected to the normally-open contact of a two-point key, K, said key itself being connected with the line N through an electro-magnetic sig nal-bel], T, of the usual construction, and the pivot of a lever, H, which latter is itself in electrical connection with the line. The normally-closed or upper contact of the key K is connected with the ground, as indicated, so

that the bellis normally in circuit and ready for a signal from the distant station, while, if the key be depressed, the battery is connected to the line, and the bell at the distant station is operated. The apparatus at both stations is substantially the same, and the line mechanically connecting the two speaking apparatus should be a conductor or contain a conductor of electricity.

G indicates a sound chamber into which the voice of the speaker is projected, provided by preference with two sound-directing openings, one of which directs the sound-vibrations onto a diaphragm, A, and the other onto a dia phragm, B, suitably mounted.

II is a lever which rests at its longer end upon a diaphragm, A, and is connected at its shorter end to the line N, by which the vibrations are communicated to and from the diaphragm to a distant instrument.

D is an adjustable screw or other adjustable device which impinges against the diaphragm A, and serves to adjust the strain of the line N thereupon. I

The pivotal supp ort of lever H may be placed in any desired location, although I prefer to mount such fulcrum or support on a second diaphragm, B, which is affected simultaneously with A, and serves in a measure to in crease the vibrations upon the line when the apparatus is spoken into. The arrangement of the lever shown reduces the strain on diaphragm A and produces the advantages hereinbel'ore set forth. The lever itself is of met al, and is electrically connected with the line N; or it may support a conductor leading from its fulcrum to the point of attachment of the line, thus completing the circuit between the bell T and the line. This arrangement for making connection between the line and the signaling apparatus obviates any interference with the vibrations of theline that might otherwise result from such connection.

I do not limit myself to the position of the fulcrum for lever H or its equivalent, as such lever may be supported by other devices than a second diaphragm, such diaphragm being then dispensed with. Other mechanical devices might be employed in place of the lever for reducing the strain on the diaphragm, while at the same time allowing mechanical vibrations to be communicated to it; but the lever is the simplest and most feasible device for the purpose.

Vhat I claim as my invention is 1. The combination, with an acoustic or mean acoustic or mechanical telephone apparatus, of a lever, one arm of which rests upon said diaphragm, with an adjustable impinging point, while its other arm is connected with the line-wire.

4. The combination, with the diaphragm, of 5 the lever H, line N, and adjustable point D, resting on the diaphragm..

5. The combination, with the diaphragm or equivalent vibratory surface in an acoustic or mechanical telephone, of a lever interposed between said diaphragm and the line, and a second diaphragm upon which said lever is fulcrumed.

6. The combination of a line, N, two diaphragms, and a lever supported on one ofsaid diaphragms, and connected at its shorter end with the line, while its longer arm impinges against the second diaphragm.

7. The combination of the two diaphragms, the common sound-directing chamber, and a lever resting on one of said dia )hragms, and

CHARLES SELDEN.

Witnesses:

FRANK CoNRoY, Jos. H. HAMILL. 

